Spray coating control apparatus



July 21, 1970 D. w. STRAW 3, 8

SPRAY COATING CONTROL APPARATUS Filed June '2. 1968 2 Sheets-Sheet 1 711:21:). 7 40 I y, E51;

45 44 E; mvzrvron ATTORNEYS July 21, 1970 D. w. STRAW 3,521,598

SPRAY COATING CONTROL APPARATUS Filed June '2, 1968 I 2 Sheets-Sheet 272 74 "4 f I RF'F 98 9 66 52 ,uo 7a 82 86 I so I e4 94 Z NAND "a I ITIMER 35 us NAND NOR m I00 I08 68 R I -ss OFF 40 FF 88 90 J -H8 I ,.sI02 I06) MANUAL l LINEIIGO N I LINEIOBO LINE I04!) I SPRAY -INES sa-IdoLINES 90-92 LINE 84 LINE 80 LINE4O LINES IlO-Il4 LINE 78 LINE 32 CYCLETIME I TO I 2 a 4 3 1 a 9 I0 II I2 l3 l4 l5 I6 I [MENTOR Dorsey WayneStraw F|G.4. BY W ATTORNEYS United States Patent 3,521,598 SPRAY COATINGCONTROL APPARATUS Dorsey Wayne Straw, Richmond, Va., assignor toReynolds Metals Company, Richmond, Va., a corporation of Delaware FiledJune 7, 1968, Ser. No. 735,306 Int. Cl. Bc 11/00 US. Cl. 1l82 22 ClaimsABSTRACT OF THE DISCLOSURE A device for spray-coating cans wherein aspray control valve is turned on by a first solenoid and turned off by asecond solenoid. Each can is passed through a cycle of operation whichincludes precoating and coating steps. A first signal is generated whena given can is in the proper portion of its cycle to be coated; and asecond signal is generated to indicate that a can is in fact in thecoating position. A gating means is operative response to thesimultaneous occurrence of the first and second signals to both actuatethe ON solenoid so as to begin the spraying operation and turn on atimer which generates a timing signal at the end of a selected time forthe can to be sprayed. The timing signal then actuates the OFF solenoidso as to terminate that cans spraying operation. The time at which thetiming pulse is generated is selectively variable without requring thespraying machine to be shut down; and the spray duration is accuratelycontrolled by means of the dual solenoids.

This invention relates to apparatus for spray-coating articles andparticularly to an apparatus for spraying the insides of rapidlyspinning cans with a thermoplastic or other plastic material dissolvedin an organic solvent.

The Food and Drug Administration requires the insides of certain typesof cans to be coated with various types of materials to prevent thecontents of the cans from being contaminated. In this respect, theacceptability of a given cans interior coating is tested by filling thecan with water; inserting a probe therein; and measuring the electricalconductivity between the probe and the outside of the can. As a resultof these tests, it has been determined that various types of cans musthave various coating weights depending upon the type of material to becontained therein. One such requirement calls for each can to have itsinterior coated with a minimum of 175 milligrams of thermoplasticmaterial. Some of the presently available spraying systems, however, areunable to stay within the allowable tolerances so that cans arepresently being sprayed with a median of 230 milligrams of coatingabout55 milligrams of overspray. Consequently, it is an object of thisinvention to provide a spraying mechanism for more accuratelycontrolling the amount of coating that is sprayed at any given time.

Presently available coating mechanisms have the spray durations thereofcontrolled by devices which sense the location of certain spray machinemechanisms, such as cams, which travel through defined paths during agiven indexing cycle of the spray machines operation. Generallyspeaking, therefore, it is necessary to terminate the operation of aspray machine in order to adjust the duration of its spraying time. Itis another object of this invention, therefore, to provide a sprayduration control means whereby the spray duration can be selectivelyvaried without requiring the spray mechanism to be shut down.

Present can spraying devices actuate a spray control valve by means of asolenoid which, in turn, is turned on and off by signals received fromproximity sensors located on relatively adjustable probes adjacent asuitably 3,521,598 Patented July 21, 1970 lobed timing cam or the like.In accordance with principles of the instant invention, on the otherhand, a spray control valve is placed in its ON position by a firstsolenoid which is operative in response to signals indicating that theappartus is in a proper portion of its cycle for a can to be sprayed andthat a can is, in fact, in the spray position. The spray control valveis placed in its OFF position by means of a second solenoid which isoperative in response to a signal from an independent timer whichgenerates an OFF signal at a selected time after the ON solenoid hasbeen actuated. In this manner, the median over-spray has been reduced to5 milligrams which, at present prices represents a savings ofapproximately onehalf million dollars per year per 5 billion cans.Moreover, because the timing means is independent of the spraymechanisms indexing system, the spray time duration can be selectivelyvaried without turning otf the entire spraying machine.

The foregoing and other objects, features, and advantages of thisinvention will be apparent from the following more particulardescription of preferred embodiments thereof as illustrated in theaccompanying drawings wherein the same reference numerals refer to thesame parts throughout the various views. The drawings are notnecessarily intended to be to scale, but rather are presented so as toillustrate the principles of the invention in clear form.

In the drawings:

FIG. 1 is a schematic illustration of an indexing mechanism forpositioning and rapidly spinning a can to be coated at a sprayingposition;

FIG. 2 is a schematic illustration of a spinning can being sprayed by amechanism having a main valve thereof controlled by two separate ON andOFF solenoids.

FIG. 3 is a schematic diagram of a logic circuit including anindependent timer mechanism for controlling the ON and OFF solenoids ofFIG. 2;

FIG. 4 is a timing diagram for the apparatus illustrated in FIG. 3.

In FIG. 1, cans to be coated travel down a shoot 10 to an indexing wheel'12 which picks up the cans in recesses thereof. The indexing member isrotatable on a shaft 16 which is schematically illustrated as beingextended through a dwell mechanism, not shown, to a cam 18'.

In a known conventional spray mechanism, the cam 18 has a variably sizedportion 20 thereof located so as to rotate under relatively adjustablesensors 22 and 24. In the past, these sensors have been either of themagnetic proximity type or micro switches operative in response tovariably located lobe on the cam 18 or other such devices. In theserespects, the probes 22 and 24 have been relatively adjustable back andforth in a slot 26 by means of suitable fasteners 28. In the instantapparatus, the probes 22 and 24 are eliminated in favor of a singleproximity sensor 30. This sensor produces an output signal on line 32when the leading edge 34 of a metallic strip 35 passes thereunder. Thissignal from the proximity sensor 30 terminates when trailing edge 36 onthe metal strip 35 passes under the sensor. In this respect, althoughnot illustrated, the speed of the timing cam 18 is suitably reduced withrespect to the indexing element 12 so that the timing cam makes acomplete revolution for each can that passes down the shoot 10 and intoa pocket on the indexing member 12. Between the time a can such as 36leaves a path position corresponding to location 14a in FIG. 1, until itis about to leave a position corresponding to location 1417, the cam 18makes one complete revolution. In thusly moving from location 14a tolocation 1417, each can passes under a second proximity sensor 3-8 whichprovides a signal on line 40 in response to the passage of a canthereunder. AS each can arrives at sta- 3 tion 14b, it engages with andis rapidly spun by a friction wheel 42. As each can is spun by the wheel42, it is sprayed with a suitable thermoplastic material 44 (FIG. 2)forced through a nozzle 46 under control of a valve mechanism 48: whichwill now be described.

The valve mechanism 48 is schematically illustrated in FIG. 2 andincludes a main valve 50 in a housing 52 for directing the flow of airand epoxy or the like entering in lines 56 and 58, respectively, andbeing passed to the nozzle 46 through line 60. In this regard, thethermoplastic material is delivered to the valve mechanism at acontrolled temperature and pressure so that the amount of spray leavingthe valve 46 is controlled by the duration that air flows from line 56to valve 50'. I

The main valve 50 is controlled by pilot valves 62 and 64 which, inturn, are controlled by solenoids 66 and 68, respectively. That is, whensolenoid 66 is energized, it causes pilot valve 62 to move an amountsufficient to cause the main valve 50 to permit air to flow through line56 and out line 60 so that the outfiowing air carries with it a meteredamount of thermoplastic material from line 58. Similarly, when solenoid68 is energized, the pilot valve 64 is moved sufliciently so as to causethe main valve 50 to close so that the flow of thermoplastic materialfrom the nozzle 46 terminates. The main valve 50 is structured so thatit remains in its last position even though the solenoids 66 and 68 aredeenergized. After each can is sprayed, the indexing wheel 12 is againmoved so as to bring another can into position at pocket 14b and so :onacoated can being delivered to an exit shoot 70 at the termination ofeach of the above described machine cycles.

Having described the mechanical aspects of the inventions structure, itselectrical control aspects will now be described. In this respect, FIG.3 is a schematic illustration of a logic diagram that is suitable foruse with the invention. NOR logic has been found to be preferable andwill be used in describing the invention. But it will be appreciated bythose skilled in the art that positive. logic can also be used. In thisregard, it should be appreciated that negative or NOR logic is basedupon the premise that a logical 1 input to any one or more of the inputsof a given NOR logic block produces a logical output.

With reference to the FIG. 3 circuit, a signal from the proximity sensor(FIG. 1) is delivered on line 32 to both an inverter 72 and the setposition of a conventional bistable flip-flop (FF) 74. The output fromthe sensor 38 on line for indicating the entry of a can into thespraying pocket 14b, on the other hand, is delivered to the set side ofa second bistable flip-flop 76. Olutputs on lines 78 and 80 from thebistable FFs 74 and 76, respectively, are delivered to a NAND gate 82which is adapted to produce an output on line 84 to a NOR gate '86.

The output from the proximity sensor 38 on line 40 indicates that a can36 has passed into position at location 14b so as to be spun by thefriction wheel 42. A signal on line 32 indicates that the cam 18 and theindexing mechanism are in a proper position to be sprayed. Consequently,logical ls appear at the set sides of the FFs 74 and 76; and because NORlogic is employed, logical Os appear on lines 78 and 80 so as to producea logical 1 output on line 84 from NAND gate 82. Hence, when the machineis at the proper portion of its cycle and a can is, in fact, positionedso as to be sprayed, simultaneous signals are delivered on lines 32 and40 to result in an output on line 84 to NOR gate 86. The NOR gate alsohas a provision for a manual input on line 88 which can be used toinitiate a test spraying operation in connection with an independenttiming means which will not be described.

When NOR gate 86 receives an input on either of lines 84 or 88, itproduces a logical 0 output on lines 90 and 92 to an independent timer94 and a second NAND gate 96, respectively. The timer is operative uponreceipt of the 0 signal on line 90 to prepare to produce subsequent 1outputs on lines 98- and 100 at a selected, predetermined time afterreceipt of the 0 pulse on line 90. In this respect, the timer 94 ispreferably of the unijunction type and is adapted to have the time ofits output independently varied by means of a suitable potentiometer102, or the like. Without regard to the period of the timer 94, however,its output on line 98 is a logical 0 at the time it receives its 0 inputon line 90*. Consequently, when the timer is placed into operation, theinputs on lines 92 and 98 to the NAND gate 96 are both 0 whereby, byvirtue of the preferred embodiments NOR logic, the NAND gate 96 producesa 1" output on line 104 to the spray valves ON solenoid 66. Thisactuates pilot valve 62 which, in turn, actuates the main valve 50 andthe can 36s spraying step is initiated.

Depending upon the timers period, as determined by the setting of thepotentiometer 102, the timer subsequently produces l timing pulses onlines 98 and 100 for delivery to the NAND gate 96 and a single shotmultivibrator (SS) 106. As soon as the NAND gate 96 receives the 1pulse, its output on line 104 is terminated and the solenoid 66 isdeenergized. At the same time, SS 106 is operative in response toreceipt of its 1 pulse to generate a signal on line 108 for energizingthe OFF solenoid 68 which, in turn, actuates the pilot valve 64 to closethe main valve 50 and terminate the spraying operation whollyindependently of the present position of the cam 18.

The structure and operation of the invention will now be described inconnection with the timing diagram of FIG. 4. As can 36 moves down theshoot 10, it was engaged by the indexing wheel 12. As the can approacheslocation 14b, the proximity sensor 38 generates a pulse (T on line 40indicating the presence of a can at loca tion 14b. Inasmuch as thissignal is delivered to the set side of PF 76, therefore, the outputthereof on line drops from a 1 to a 0 at T Thereafter, the leading edge34 of metallic strip 35 on the cam 18 passes under the proximity sensor32 to produce a 1 pulse at time 3 (T as illustrated in FIG. 4. Inasmuchas this signal is delivered to the set side of PF 74, therefore, theoutput from the FF on line 78 drops to a 0 level at T and the outputfrom inverter 72 on line 110 also drops to 0,

but has no affect upon a SS 112 to which it is delivered. At Ttherefore, NAND gate 82 is provided with two 0 inputs and, by virtue ofthe preferred embodiments use of NOR logic, the NAND gate 82 provides a1 output on line 84 at T which causes NOR gate 86 to provide a 0 outputon lines and 92, also at T The pulse on line 90 at T causes the timer 94to start running in preparation for the subsequent generating of atiming signal on lines 98 and at a time to be determined by the settingof rheostat 102. Until such time as that timing signal is generated,however, the output on line 98 remains a 0. Hence, at T NAND gate 96receives two 0 inputs so as to produce one output on line 104 whichenergizes the ON solenoid 66 in FIG. 3.

When the solenoid 66 is energized, the pilot valve 62 (FIG. 2) isactuated causing the main valve 50 to be opened to air pressure fromline 56 which draws thermoplastic coating from line 58 and forces itthrough line 60 and nozzle 46 so as to coat the inside of the can 36which is being spun by friction roller 42. This spray operation isaccomplished quite irrespective of inaccuracies in the signals comingfrom the proximity sensors 30 or 38. This is due, at least in part, tothe fact that the proximity signals are used only for a starting pointof operation. The timing network controls the length of the period ofspraying. Once the main valve 50 is actuated into the spray position bythe ON solenoid 66, it can only be returned to its OFF position inresponse to actuation of the OFF solenoid 68 whose operation, as willnow be described, relies only upon an output from the timer for itsenergization.

At the selected time, as determined by the setting of rheostat 102 (T(in the illustrated embodiment), the timer 94 generates a pulse on lines98 and 100 causing the line 104 signal to drop to 0 and SS 106 toproduce a 1 pulse on line 108 so as to energize the OFF solenoid 68. AtT therefore, energization of the OFF solenoid actuates pilot valve 64which, in turn, causes the main valve to close olf the air inlet 66 andthereby terminate the spray of thermoplastic material from the nozzle46. At some suitable time thereafter, in a conventional manner, theindexing means 12 moves the can 36 onwardly toward the exit shoot 70 andpositions the next can at the spraying pocket 14b.

If inspection of the can 36 indicates that more or less than the desiredamount of thermoplastic spray was deposited on the cans interior, it ismerely necessary to adjust the rheostat 102 without requiring themachine to be shut down so as to permit changes in the relative location of probes 22 and 24 and lobes such as might occur on cam 18 (FIG.1). Moreover, by using a dual solenoid operated valve such as 50, theinaccuracies of a single spring returned solenoid or valve are avoided.In these respects, it should be noted that the instant device permits areduction of over 90% in the amount of overspray that has previouslybeen required on the interiors of cans with which the invention has beenemployed.

In accordance with a still further aspect of the invention, the SS 106is included in the timing circuit so as to prevent objectionable andwasteful blow-by of air past the pilot valve 64 when the OF solenoid 68is energized. That is, many conventional solenoid actauted pilot valvessuch as '64 permit high pressure air (such as from a bleed lineillustrated in phantom between inlet line 56 and pilot valve 64) to blowpast the pilot valve so as to actuate the main valve. Consequently, anytime the OFF solenoid 68 is energized, high pressure air blows by thepilot valve 64. For this reason, and inasmuch as the main valveautomatically retains the position to which it was last set, the OFFsolenoid 68 is energized by SS 106 rather than being merely energizedwhenever the ON solenoid is deenergized. This is illustrated in FIG. 4where the SSs output on line 108 drops to its 0 level at T Looking backnow to T in FIG. 4, it can be seen that the signal on line 40 from theproximity sensor 38 dropped shortly after the can 36 passed. Inasmuch asno subsequent significant signal was received by the PF 76, however, itsoutput on line 80 remained at its 0 level. But at T the trailing edge 36on the cam 18s metal strip (FIG. 1) passed under the proximity sensor 30so as to drop the signal on line 32. This causes the inverter 72s outputon lines 110 and 114 to rise so that FF 74 is reset placing a 1 signalon line 78; and causing SS 112 to produce an output on line 116 forresetting FF 76 so as to return line 80 to its 1 level at T The NANDgate 82s output on line 84 also drops to O at T which causes the outputof NOR gate 86 on lines 90 and 92 to return to the 1 level. The timer 94is also reset by a suitable pulse on line 118 at T The timer reset pulseon line 118 can be derived from any suitable source such as from NOR 86,for example.

By T the output from SS 112 on line 116 has returned to its 0 level andthe entire circuit has returned to its starting point so as to beprepared for the next cycle of operation which is initiated by the nextcycletime pulse from the proximity sensor 30 on line 32 as illustratedin FIG. 4 at T It will be appreciated by those skilled in the art thatthe above structure provides a spray mechanism for accurately selectingthe duration that a given article is to be sprayed so that the weight ofsprayed material can be accurately controlled and the amount ofover-spray reduced to a more practical minimum. Moreover, it will beappreciated that the spray duration can be selectively 6 varied withoutrequiring the entire spray apparatus to be shut down; and still further,it should be noted that the use of a separate energization means such asSS 106 for the OFF solenoid 68 permits a reduction in the amount ofobjectional blow-by from the pilot valve associated with the OFFsolenoid.

While the invention has been particularly shown and described withreference to a preferred embodiment thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade therein without departing from the spirit and scope of theinvention. For example, although the operating circuit was described inconnection with NOR logic, it should be clear that positive logic couldalso be used. Similarly, although the invention has been described inconnection with the spraying of can interiors, the structure of theinvention can be used for spraying other articles such as might berequired in the refinishing of integrally riveted can ends, for example.

The embodiments of the invention in which an exclusive property orprivileges claimed are defined as follows:

1. In an apparatus for spray-coating articles wherein each such articleto be spray-coated is sequentially moved in a cycle from a precoatingposition to a coating position and then to a postcoating position, thecombination comprising:

means for producing a first signal when said apparatus begins thecoating portion of said cycle;

means for generating a second signal in response to the presence of anarticle in said coating position;

selectively operable spraying means for selectively spray-coating saidarticle;

timing means;

gating means operative in response to said first and second signals forgenerating a gating signal to initiate operation of said spraying meansand said timing means, said timing means being operative to generate atiming signal a selected time after being turned on; and

means operative in response to said timing signal for turning off saidspraying means.

2. The apparatus of claim 1 wherein said spraying means is comprised of:

a nozzle having the flow of coating material therethrough controlled bya main valve having an ON position and an OFF position;

first and second pilot valves operative upon actuation to place saidmain valve in said ON and said OFF positions, respectively;

a first pilot valve actuating means for actuating said first pilot valveand a second pilot valve actuating means for actuating said second pilotvalve;

means for delivering said gating signal to said first actuating meansand means for delivering said timing signal to said second actuatingmeans, said first actuating means being operative in receipt of saidgating signal to actuate said first pilot valve so that said main valveis placed in said ON position; and

said second actuating means being operative in response to said timingsignal to actuate said second pilot valve for placing said main valve insaid OFF position.

3. The apparatus of claim 2 including a means for delivering said timingsignal to said first actuating means, said first actuating means beingoperative in response to receipt of said timing signal to deactuate saidfirst pilot valve.

4. The apparatus of claim 2 wherein said first and second actuatingmeans are comprised of solenoids.

5. The apparatus of claim 2 wherein said second actuat ing meansincludes a solenoid and energizing means operative in response toreceipt of said timing signal for energizing said solenoid.

6. The apparatus of claim 5 wherein said energizing means is comprisedof a single shot multivibrator.

7. The apparatus of claim 1 wherein said timing means includes means forselectively varying the time duration between the initiation of theoperation thereof and the generation of said timing signal.

8. The apparatus of claim 7 wherein said spraying means is comprised ofa nozzle having the flow of coating material therethrough controlled bya main valve having an ON position and an OFF position;

first and second pilot valves operative upon actuation to place saidmain valve in said ON and said OFF positions, respectively;

a first pilot valve actuating means for actuating said first pilotvalve; and a second pilot valve actuating means for actuating saidsecond pilot valve;

means for delivering said gating signal to said first actuating meansand means for delivering said timing signal to said second actuatingmeans, said first actuating means being operative on receipt of saidgating signal to actuate said first pilot valve so that said main valveis placed in said ON position; and

said second actuating means being operative in response to said timingsignal to actuate said second pilot valve for placing said main valve insaid OFF position.

9. The apparatus of claim 8 including a means for delivering said timingsignal to said first actuating means, said first actuating means beingoperative in response to receipt of said timing signal to deactuate saidfirst pilot valve.

10. The apparatus of claim 8 wherein said first and second actuatingmeans are comprised of solenoids.

11. The apparatus of claim 8 wherein said second actuating meansincludes a solenoid and energizing means operative in response toreceipt of said timing signal for energizing said solenoid.

12. The apparatus of claim 11 wherein said energizing means is comprisedof a single shot multivibrator.

13. The apparatus of claim 1 wherein said means for producing saidsecond signal includes a proximity sensor and a bistable flip-flop, saidproximity sensor being operative in response to the proximity of anarticle to be coated for generating a SET signal to said flip-flop, andsaid flip-flop being operative in response to receipt of said SET signalfor generating said second signal.

14. The apparatus of claim 13 wherein said first signal producing meansincludes a means for generating a cycletime signal when said apparatusis adapted to position an article at said coating position;

a second flip-flop and means for delivering said cycletime signal to aSET input on said second flip-flop to produce said first signal at anoutput of said flip-flop.

15. The apparatus of claim 14 including a means for resetting the firstand second flip-flops.

16. The apparatus of claim 15 wherein said reset means is comprised of:

an inverter;

a single shot multivibrator;

means for delivering said cycle-time signal to said inverter; means fordelivering the output of said inverter to:

(i) a reset input on said second flip-flop; and (ii) said single shotmultivibrator; and

means for delivering an output signal from said single shotmultivibrator to a reset input on said flip-flop. 17. The apparatus ofclaim 16 wherein said timing means includes a means for varying the timeduration between receipt of said signal from said gating means and thegeneration of said timing signal;

a reset means; and

means for delivering said output signal from said single shotmultivibrator to said timer reset means for resetting said timer.

18. The apparatus of claim 14 wherein said spraying means is comprisedof:

a nozzle having the flow of coating material therethrough controlled bya main valve having an ON position and an OFF position;

first and second pilot valves operative upon actuation to place saidmain valve in said ON and said OFF positions, respectively;

a first pilot valve actuating means for actuating said first pilotvalve; and a second pilot valve actuating means for actuating saidsecond pilot valve;

means for delivering said gating signal to said first actuating meansand means for delivering said timing signal to said second actuatingmeans, said first actuating means being operative in response to receiptof said gating signal to actuate said first pilot valve so that saidmain valve is placed in said ON position; and

said second actuating means being operative in response to said timingsignal to actuate said second pilot valve for placing said main valve insaid OFF position.

19. The apparatus of claim 18 including a means for delivering saidtiming signal to said first actuating means, said first actuating meansbeing operative in response to receipt of said timing signal todeactuate said first pilot valve.

20. The apparatus of claim 18 wherein said first and second actuatingmeans are comprised of solenoids.

21. The apparatus of claim 18 wherein said second actuating meansincludes a solenoid and energizing means operative in response toreceipt of said timing signal for energizing said solenoid.

22. The apparatus of claim 21 wherein said energizing means is comprisedof a single shot multivibrator.

References Cited UNITED STATES PATENTS 2,103,270 12/1937 Murch 11s 31s X3,356,061 12/1967 Wiggins 118-2 JOHN P. McINTOSH, Primary Examiner US.01. X.R. 00 11s 9, 31s

